Account for preload changes in the left ventricle

Abstract

A method of estimating a patient's cardiac preload in a patient having an implantable blood pump. The method includes generating a current waveform from operation of the implanted blood pump. A beat-to-beat pump filling index (PFI) is calculated, the PFI is calculated by dividing a current amplitude component by a time component, the amplitude component being calculated by subtracting a trough of the current waveform from an inflection point divided by an amplitude difference of peak to trough of the waveform, the time component being calculated by dividing a time between the trough and the inflection point by a time between the peak and the trough. An alert is generated if the PFI deviates from predetermined thresholds.

What is claimed is: 
     
         1 . A method of estimating a patient's cardiac preload in a patient having a blood pump, the method comprising:
 generating a current waveform from operation of the blood pump;   calculating a beat-to-beat pump filling index (PFI), the PFI being calculated by dividing a current amplitude component by a time component, the amplitude component being calculated by subtracting a trough of the current waveform from an inflection point divided by an amplitude difference of peak to trough of the current waveform, the time component being calculated by dividing a time between the trough and the inflection point by a time between the peak and the trough; and   generating an alert if the PFI deviates from predetermined thresholds.   
     
     
         2 . The method of  claim 1 , wherein the predetermined thresholds include an upper threshold and a lower threshold different than the upper threshold. 
     
     
         3 . The method of  claim 2 , wherein generating the alert comprises generating the alert in response to determining a median PFI calculated from a prior 5 consecutive beat-to-beat calculations of the PFI is greater than the upper threshold or lower than the lower threshold. 
     
     
         4 . The method of  claim 3 , further including increasing a speed of an impeller of the blood pump if the median PFI exceeds the upper threshold. 
     
     
         5 . The method of  claim 3 , further including decreasing a speed of an impeller of the blood pump if the median PFI drops below the lower threshold. 
     
     
         6 . The method of  claim 3 , wherein the upper threshold is determined by:
 multiplying a twentieth percentile of the PFI from a prior 10 consecutive beat-to-beat calculations of PFI by 1.2; and wherein the lower threshold is determined by:
 multiplying an eightieth percentile of the PFI from the prior 10 consecutive beat-to-beat calculations of PFI by 0.8. 
   
     
     
         7 . The method of  claim 1 , further comprising recording and displaying the alert in a log-file. 
     
     
         8 . The method of  claim 1 , further including increasing or decreasing a speed of an impeller of the blood pump based on the alert. 
     
     
         9 . The method of  claim 8 , wherein the increasing or decreasing of the speed of the impeller of the blood pump is either automatic or clinician initiated. 
     
     
         10 . The method of  claim 1 , wherein the alert is indicative of either a high cardiac preload or a low cardiac preload. 
     
     
         11 . A controller for a blood pump, the controller comprising:
 processing circuitry configured to:   generate a current waveform from operation of the blood pump; calculate a beat-to-beat pump filling index (PFI), the PFI being calculated by   dividing a current amplitude component by a time component, the amplitude component being calculated by subtracting a trough of the current waveform from an inflection point divided by an amplitude difference of peak to trough of the current waveform, the time component being calculated by dividing a time between the trough and the inflection point by a time between the peak and the trough; and   generate an alert if the PFI deviates from predetermined thresholds.   
     
     
         12 . The controller of  claim 11 , wherein the predetermined thresholds include an upper threshold and a lower threshold different than the upper threshold. 
     
     
         13 . The controller of  claim 12 , wherein the processing circuitry is configured to generate the alert in response to determining a median PFI calculated from a prior 5 consecutive beat-to-beat calculations of the PFI is greater than the upper threshold or lower than the lower threshold. 
     
     
         14 . The controller of  claim 13 , wherein the processing circuitry is further configured to increase a speed of an impeller of the blood pump if the median PFI exceeds the upper threshold. 
     
     
         15 . The controller of  claim 13 , wherein the processing circuitry is further configured to decrease a speed of an impeller of the blood pump if the median PFI drops below the lower threshold. 
     
     
         16 . The controller of  claim 12 , wherein the processing circuitry is configured to determine the upper threshold by at least multiplying a twentieth percentile of the PFI from a prior 10 consecutive beat-to-beat calculations of PFI by 1.2, and wherein the processing circuitry is configured to determine the lower threshold by at least multiplying an eightieth percentile of the PFI from the prior 10 consecutive beat-to-beat calculations of PFI by 0.8. 
     
     
         17 . The controller of  claim 11 , wherein the processing circuitry is configured to increase or decrease a speed of an impeller of the blood pump based on the alert. 
     
     
         18 . A controller for a blood pump, the controller comprising:
 processing circuitry configured to:   generate a current waveform from operation of the blood pump;   calculate a beat-to-beat pump filling index (PFI), the PFI being calculated by   dividing a current amplitude component by a time component, the amplitude component being calculated by subtracting a trough of the current waveform from an inflection point divided by an amplitude difference of peak to trough of the current waveform, the time component being calculated by dividing a time between the trough and the inflection point by a time between the peak and the trough; and   increase or decrease a set speed of an impeller of the blood pump if the PFI deviates from a predetermined threshold.   
     
     
         19 . The controller of  claim 18 , wherein the processing circuitry is configured to increase or decrease the set speed of the impeller by at least increasing the speed of the impeller if the PFI exceeds the predetermined threshold. 
     
     
         20 . The controller of  claim 18 , wherein the processing circuitry is configured to increase or decrease the set speed of the impeller by at least decreasing the speed of the impeller if the PFI is less than the predetermined threshold.